1. Field of the Invention
The present invention generally relates to coating apparatus used to apply synthetic resin, bonding or other agents to a web of sheet material such as paper and plastic film and more particularly, to an improved coating apparatus which enables rapid and ready change of coating methods such as a bottom reverse coating method and a top reverse coating method.
2. Description of the Related Art
FIGS. 12(A) and 12(B) schematically show typical coating methods by the use of three rolls B, C and M. Such methods include a bottom reverse coating method used to apply a low viscosity coating agent (see FIG. 12(A)), and a top reverse coating method used to apply a high viscosity coating agent (see FIG. 12(B)). The reference sign T designates an imaginary triangle which connects the axes of the three rolls B, C and M. In the bottom reverse coating method, the imaginary triangle is in a normal position, whereas in the top reverse coating method, the imaginary triangle T is in an inverted position. Thus, the imaginary triangle is rotated at an angle of about 40 to 45 degrees when a change of these methods takes place. The rolls B and M need be moved away from and toward the roll C. When the rolls B and M are moved toward the roll C to apply a coating agent, a required space must be kept between the rolls B and M and the roll C. In FIGS. 12(A) and 12(B), the reference signs A and S designate a coating agent and a web of sheet material, respectively.
However, no mechanism has heretofore been proposed to change the position of bearings for the rolls B and M so as to rotate the imaginary triangle T by an angle of about 40 to 45 degrees. To that end, a plurality of separate coating apparatus need be provided to perform various coating methods so as to apply coating agents having different viscosities or other properties.
The provision of separate coating apparatus is costly and consumes substantial floor space. Accordingly, it is an object of the present invention to overcome these problems and provide a coating apparatus which can readily and rapidly change the orientation of an imaginary triangle which connects the axes of three rolls, in response to types of coating agents.